Epitrochoid

An epitrochoid (/ɛpᵻˈtrɒkɔɪd/ or /ɛpᵻˈtroʊkɔɪd/) is a roulette traced by a point attached to a circle of radiusr rolling around the outside of a fixed circle of radius R, where the point is at a distance d from the center of the exterior circle.